The invention relates generally to milling cutters and, more particularly, relates to an end milling cutter having a square footprint and capable of cutting a ninety degree shoulder in a workpiece.
Milling is a cutting machining process using a rotating tool. In that procedure, the cutting edges produce the cutting movement by virtue of their rotation about the central axis of the tool. The advance movements can take place in various directions. They are effected by the tool or by the workpiece or even by both. In contrast to turning and drilling, the cutting edges are not constantly in engagement. After a cut on the workpiece, they are returned in the disengaged condition to the point of first cut. As a result, they can cool down and discharge the chips from the chip spaces.
In principle, a distinction is made between three different milling cutting processes: peripheral milling, end milling and end-peripheral milling. Peripheral milling, also referred to as hob milling, is a milling process in which the major cutting edges which are at the periphery of the tool generate the desired workpiece surface; the milling cutter axis therefore extends parallel to the working surface and perpendicularly to the advance direction of the milling cutter. In the end milling process, the desired workpiece surface to be produced is that to which the milling cutter axis is perpendicular, and in that case, the advance direction of the milling cutter is parallel to the workpiece surface produced. In that case, however, essential chip removal is also effected primarily with the major cutting edges arranged at the peripheral surface. The minor cutting edges which are at the end of the tool smooth the milled surface, and thus produce the workpiece surface. Finally, in end-peripheral milling, both the major and also the minor cutting edges produce the desired workpiece surfaces.
Relatively high-grade surfaces can be produced by means of end milling. In that respect, the minor cutting edges are solely responsible for the surface produced. They move in one plane and not on a curved working surface like the major cutting edges that generate the workpiece surface in peripheral milling. Fine final machining of flat surfaces is possible with suitable end milling cutters. The general view is that the quality of the particularly flat and smooth surfaces produced by end milling is essentially determined by the cutting edge corner shape and by the orientation of the minor cutting edges.
A conventional milling cutter 100 is shown in FIGS. 5-7. In the conventional milling cutter 100, a cutting portion 104 has a plurality of major cutting edges 106 that are separated from each other by a corresponding number of spiral flutes 108. The milling cutter 100 shown in FIG. 4 has two major cutting edges 106 and two spiral flutes 108. The milling cutter 100 shown in FIGS. 5-7 has four major cutting edges 106 and four spiral flutes 108. Peripheral surface sections of the cutting portion 104 define a cylindrical envelope surface 109 of the cutting portion 104. The end face 117 of the cutting portion 104 have minor cutting edges 107.
As shown in FIG. 5, the conventional milling cutter 100 also includes a primary clearance face 110, a secondary clearance face 112 and a chip gash 114. In addition, an end portion 120 of the minor cutting edges 107 of conventional milling cutter 100 has a hook-shape when viewed from the end face 117, as highlighted in FIG. 6.
The milling cutter 100 rotates about a central, longitudinal axis 116, as shown in FIG. 6. Specifically, the milling cutter 100 shown in FIG. 6 rotates in a counter-clockwise direction about the central, longitudinal axis 116.
As seen in FIGS. 6 and 7, the corner 118 of the conventional milling cutter 100 is not formed at an angle of 90°, but at an angle other than 90°. As a result, the conventional milling cutter 100 cuts a shoulder in the workpiece 200 at an angle 132 that is not exactly equal to 90°, but rather produces a chamfer in the workpiece 200. Further, the conventional milling cutter experiences a very short tool life when attempting to cut a 90° shoulder in the workpiece 200. Unfortunately, there are numerous metal cutting applications in which it would be desirable to cut a 90° shoulder in a workpiece.